The invention generally relates to a film used to provide labels that are removable, and more specifically but without limitation, to a film used to provide patch labels that are removable, including both clear and opaque patch labels, to be used with a water-based adhesive.
Glass or plastic bottles and other containers exist in a large variety of sizes and shapes for storing a multiplicity of materials including motor oil, detergents, food and drink, and more. Given the variety of end-uses, it is often desirable to place a label on the container to advertise and promote, or simply identify the ingredients of, the product therein.
Throughout the years, a number of materials have been used to provide labels for containers, including many types of paper and polymer film. There are many factors to consider when choosing between paper and polymer film, or between types of paper or types of film, as the material for making a label.
Depending on the intended application, one factor in choosing a material to make a label is the desired properties of the label, including durability, moisture resistance, curl resistance, abrasion resistance, initial adhesion strength, or the ability to delaminate (sometimes referred to as “fiber tear”). Another factor is the compatibility of the label with the intended adhesive. The final choice of material is often a fine balance between cost and the capability of the selected material to possess the desired properties for the particular end-use in mind (labels for glass v. plastic containers; labels for cold temperature v. room-temperature or warm temperature environments; labels for humid v. dry environments).
Recently, a new factor has emerged that impacts the choice of material for labels. Re-usable containers, such as re-usable beverage bottles, are a hot commodity in European markets, and are gaining in popularity in the North American market. It is becoming increasingly important for containers to be both re-usable and re-cyclable and for the labels thereon to function accordingly, in particular with respect to bottles and other containers for the beverage market.
While re-cyclable containers are simply crushed prior to the re-cycling process, a container that is both re-usable and re-cyclable must be able to withstand several cycles of cleaning and refilling prior to being crushed and entering the re-cycling process. In addition, the label(s) on a container that is returned for re-use must be able to be completely removed in a solution, e.g., a warm caustic solution, in order for the container to be cleaned and refilled. Of course, the label of a re-usable container must also be able to maintain other desired properties, such as strong initial adhesion strength, moisture resistance, and delaminatability.
A paper label attached to a container, such as a beverage bottle, by a water-based adhesive can be relatively easily and completely removed by submerging the container in a caustic solution. Paper is the standard in the industry and typically demonstrates removability in less than three minutes in hot caustic solution. There are disadvantages to using paper labels, however, including the fact that their physical characteristics tend to deteriorate in a high humidity environment, among other disadvantages.
Many polymer film labels possess a strong resistance to moisture. Due to the inherent barrier properties of their polymer composition, the polymer film labels presently known in the art cannot be easily and completely removed from a container simply by submerging the labeled container in a hot caustic solution, as compared to paper labels.
U.S. Pat. No. 6,517,664 to Dronzek, Jr. discloses a technique for labeling a container or surface with a polymer label. The disclosed labels are adapted to facilitate the re-cycling process. The adaptation in the '664 patent, however, concerns the selection of a low density polymer material to provide the label, wherein the disclosed polymer material has a density within a particular range and is specifically chosen from among polyethylene, polyester, polystyrene, polycarbonate, and compatibilized polymer blends.
U.S. Pat. No. 6,306,242 to Dronzek and U.S. Patent Application Publication 2001/0035265 to Dronzek both disclose techniques for labeling a container with a polymer label, wherein the label does not have to be removed from the container in order to re-cycle or re-grind the post-consumer container.
Films comprising a polylactic acid-type polymer are known. For example, U.S. Pat. Nos. 6,326,440 to Terada, et al., 6,235,825 to Yoshida, et al., U.S. No. 6,156,929 to Chandler, et al., 5,866,634 to Tokushige, et al., U.S. Pat. Nos. 5,663,288 to Shinoda, et al., U.S. Pat. No. 5,851,662 to Suzuki, et al., and U.S. Pat. No. 5,422,377 to Aubert each discloses a resin composition containing a polylactic acid-type polymer for forming biodegradable films or breathable and hydrolyzable films. None of the patents, however, discloses a polymer film structure for making labels, wherein an outer layer of the film structure (i) contains a polylactic acid polymer and (ii) is adapted to contact a water-based adhesive.
There exists a need for a polymer film structure for making labels, wherein the polymer film labels can be easily and completely removed from a corresponding bottle or other container by submerging the container in a solution as part of a process to re-use the container. There further exists a need for both clear and opaque embodiments of the labels that are removable. There still further exists a need for polymer film labels that combine removability with excellent initial adhesion strength, moisture resistance, and delaminatability.